1. Field of the Invention
The present invention relates generally to engine oil monitoring devices and, more particularly, to safety devices for shutting down engine operation in the case of oil loss or excessive oil usage. Specifically, the present invention relates to an engine oil monitoring safety device which is based on monitoring the level of oil within the engine oil containment system.
2. Description of the Prior Art
Devices for monitoring engine lubrication systems are well known in the art. Typically, engines such as reciprocating engines require lubrication which is provided by oil held within a containment vessel, more commonly known as an oil pan, mounted below the engine. A cam shaft carrying the piston connecting rods passes through the oil pan. Thus, as the cam shaft is rotated thereby operating the pistons, oil is carried up to the pistons by movement of the connecting rods and cam shaft in the oil pan.
Most engines gradually use some of the oil by burning it in the ignition process. Depending on the condition of the engine, this oil usage can be very minimal or can be quite rapid. In addition, since the oil pan is mounted below the engine, there is always a possibility that the pan may develop a leak of some sort thereby eventually draining the oil from the pan. Thus, it is imperitive that the oil be monitored to insure that there is a sufficient amount of oil within the lubrication system to provide proper lubrication of the engine. To further insure that there is sufficient oil, an oil sump is generally provided as part of the oil containment vessel, the oil sump containing a reservoir of oil for usage by the engine. Without sufficient oil to lubricate the engine, heat from friction and ignition developed within the engine cylinders will quickly ruin the piston rings as well as the engine block itself.
Engine manufacturers provide an oil lubrication containment system in conjunction with the manufactured engine. Moreover, the engine manufacturers generally suggest a recommended minimum volume of oil within such systems necessary to provide proper lubrication of the engine. Inherent in such engine manufacturer recommendations is a built-in safety factor such that should the amount of oil within the engine system fall below the manufacture's recommended level, there will none the less be sufficient oil in the system to provide adequate lubrication for a period of time. However, a point is reached whereby insufficient oil is present to provide even minimally adequate lubrication, thereby permitting excessive heat to be developed within the engine which can result in the damage described above.
Most engines also include an oil pump in association with the oil containment vessel to insure that sufficient oil is pumped into the system immediately below the engine. This is achieved with the pressure developed by the oil pump. In conjunction with such oil pumps, most engines include a monitoring system based on oil pressure within the oil containment and lubrication system. The assumption behind such monitoring systems is that the oil pressure will provide adequate information to determine whether there is sufficient oil being delivered to the system to provide ample lubrication of the engine. Thus, should an oil pump fail for example, the oil pressure is reduced to zero. This informs the operator of the engine that there is no oil pressure within the oil containment vessel and therefore insufficient lubrication being provided to the engine. The operator will then shut down the engine to prevent damage. Another system based on the above includes a safety shutdown device whereby the engine will automatically be shut down should the oil pressure be reduced to zero or some other predetermined level. This eliminates the possibility of human operator error.
A significant flaw, however, has been discovered in the above described systems. It was determined that the oil pumps in some engine lubrication systems were sufficiently large in output such that the combined oil pressure and air pressure developed by the oil pump was sufficient to maintain the pressure output reading from the oil containment vessel at an acceptable level even though the actual amount of oil within the containment vessel fell below the minimum necessary to adequately lubricate the engine. Thus, the monitoring device would indicate that at the oil pressure level was adequate even though the amount of oil within the system was actually inadequate to lubricate the engine. Consequently, the false readings resulted in continued engine operation thereby causing substantial damage due to insufficient oil to lubricate the engine. As a result of the above, it became clear that the monitoring systems based solely on oil pressure were inadequate in certain instances wherein the oil pressure was not directly representative of the actual amount of oil within the oil containment and lubrication system.